I've been looking at the live mempool on mempool.space, and while most transactions are sorted in order of highest sat/vB to lowest, I've noticed some that standout with extremely high sat/vB but are placed further back in the block.

I've tried looking for reasons why, such as a parent-child dependency, but I couldn't figure it out.

What exactly determines this ordering? I'm wondering what the incentive of agreeing to a much higher rate is, if your transaction will be fulfilled later than others in the block, or potentially even pushed back to the next one.

  • You tagged the question bitcoin-core, can you confirm you want to know specifically how bitcoin core's getblocktemplate selects and orders transactions rather than how other mining software and other algorithms work? Commented Feb 26 at 10:50
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    Does this answer your question? Why does getblocktemplate use priority for transaction selection? Commented Feb 26 at 10:54
  • @RedGrittyBrick: I don’t think that’s related. Coin-age priority was disabled by default in Bitcoin Core v0.12
    – Murch
    Commented Feb 26 at 13:05
  • Pieter's answer does mention that the priority based selection was replaced by a CPFP algorithm. Commented Feb 26 at 20:09
  • @RedGrittyBrick that post helped me deepen my understanding a lot, thanks. I think my question has been answered. Additionally, I realized that I was looking at the fee rate, when the effective fee rate is what's being used to order the transactions in most cases.
    – Blank Dev
    Commented Mar 1 at 8:59


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